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I've been having an issue for some time now where the coolant gets pushed to the coolant expansion tank as it expands and is not sucked back into the radiator as it cools. I've manually drained the expansion tank back into the radiator and it does the same thing the next time I drive. My engine temps are good.

I've tried testing the radiator cap and it does seem to hold pressure and relieve around where it should be. However, it doesn't really test vacuum. The only other thought I have is a headgasket issue. I need to test the coolant for hydrocarbons....I just haven't gotten around to it. I suppose the easy test would be to replace the radiator cap first.

Any thoughts?

Every Subaru of mine that did that had blown HGs. 2 of those were even Ej22e's. One of which was from my 98 OBS.

If you carry a turkey baster around, like I did in my college days for this exact purpose, you can transfer coolant back into the radiator when it's cold. Now that I have a career I wouldn't think of doing that. The car in question (96 Legacy L) lasted like 40k miles before I replaced the engine with the vastly more reliable ej25d ;p

In the back of my head I kind of figured it would be the head gasket. When I get time or feel like it I’ll do the hydrocarbon sniffer. I’ve got another car to drive besides the Legacy so it’s not urgent....and I may be looking at something else come fall. We’ll see.

Could be a bad/clogged vacuum valve in the radiator cap that's not allowing the coolant to be drawn back into the coolant system. There are a few ways to check for excessive vacuum as the engine cools down, the easiest being doing a visual on the upper radiator hose and seeing if it appears crushed from the vacuum once cooled. Another cheap way is after the engine has cooled is to release the radiator cap and see if there is a pop or some auditory indication there is a pressure difference between the radiator and the outside atmosphere. Might be a cheap fix to check and then pick up a replacement cap to see if the issue goes away. Either that or just do a mike-tracy and swap over to the 25d since we all know they never have head gasket issues!

So I did a hydrocarbon/CO2 detector test on the cooling system yesterday and it came back good. The fluid stayed blue. I verified the fluid was still working properly. So I'm going to try a new radiator cap and see if that fixes the issue.

Did you ever find a fix for this problem. I have the same issue on my 94. Never overheats but pushes coolant.

DuceDuceTurbo wrote: ↑Wed Sep 08, 2021 2:46 am Did you ever find a fix for this problem. I have the same issue on my 94. Never overheats but pushes coolant.

Replace the hose going into the coolant bottle. Check for hydrocarbons in the coolant if that doesn't work.

DuceDuceTurbo wrote: ↑Wed Sep 08, 2021 2:46 am Did you ever find a fix for this problem. I have the same issue on my 94. Never overheats but pushes coolant.

Unfortunately I never did. I checked for hydrocarbons in the coolant and didn't find any. I sold the car to a friend and he drove it and didn't have issues. So either the coolant level dropped and is still working ok or it stopped (which probably unlikely).

Thanks for your reply. Mine is very strange as the last time I rallycrossed it she didn’t push any coolant all day then the 1 hour drive home and the coolant was almost out of the overflow. I guess I’ll keep checking. Thanks again

Yeah, mine was similar. I couldn’t really figure out what the issue was. I assume it’s probably head gasket related but was unable to definitively prove it.

If you’re able to figure out the cause and any additional details please update this post.

Thanks

My 2009 Toyota was doing the same thing. Pushing coolant and not sucking it back in. It turned out to be a blown head gasket.